What does the P-R interval include in an ECG?

The P-R interval in an electrocardiogram (ECG) specifically refers to the time period that encompasses the P wave and the PR segment. The P wave represents atrial depolarization, indicating that the electrical impulse has traveled through the atria to the AV node. Following this, the PR segment represents the time it takes for the electrical impulse to travel through the AV node, the bundle of His, and into the bundle branches, before ventricular depolarization begins.

In a normal cardiac cycle, the P-R interval provides important information about the conduction of electrical signals through the heart. It reflects how well the atria and ventricles are communicating and can be an indicator of various types of heart block if prolonged or shortened. This makes the inclusion of both the P wave and the PR segment essential to fully understanding the timing of electrical activity before the ventricles depolarize.

Thus, the correct understanding and identification of the P-R interval as consisting of the P wave and the PR segment is vital in interpreting ECGs and assessing cardiac function.